The invention relates generally to forming pumpable compositions from solid materials. More specifically, the invention relates to a fuel in the form of a pumpable fluid formed from solid carbonaceous materials.
Solid carbonaceous materials are often formed as by-products of petroleum refining and separation. De-Asphalting Unit (DAU) rock and coke formed in coking units are examples of such materials. These materials are useful as fuels for power generation and also in reactions such as hydrocarbon partial oxidation.
Solvent de-asphalting is one method for upgrading resids produced in vacuum and atmospheric pipestills. One by-product of solvent de-asphalting is deasphalting unit (xe2x80x9cDAUxe2x80x9d) rock. DAU rock is a solid carbonaceous material that has a high concentration of Conradson carbon (xe2x80x9cConcarbonxe2x80x9d) and metals. The presence of Concarbon and metals diminishes DAU rock""s usefulness as a feed for further refining and leads to very high disposal costs. However, this material is useful as a feed for power generation and for the production of CO and hydrogen, a mixture frequently referred to as syngas, from the partial oxidation of hydrocarbons such as methane.
Cokers are also used for refining resids produced in atmospheric and vacuum pipestills. Petroleum/refinery coke (xe2x80x9ccokexe2x80x9d) is the solid carbonaceous material formed in the coker. Coke generally forms in one of three solid morphologies. Most petroleum coke is formed as xe2x80x9csponge cokexe2x80x9d, a hard porous irregularly shaped material ranging in size from about 20 inches to a fine dust. Some coke is formed in the shape of very fine needle shaped particles called needle coke. The least common form of coke is xe2x80x9cshotxe2x80x9d coke, named from the clusters of shot-sized pellets in which it is most often found.
Petroleum coke does not have sufficient strength to be useful in the production of pig iron or as foundry coke. Additionally, the high concentration of metals in petroleum source results in high disposal costs. However, like DAU rock, this material is useful as a fuel for power generation and syngas production.
One problem associated with the use of coke or DAU rock as a fuel results from the logistical difficulties and high transportation costs incurred in moving the fuel from a refinery to a power plant. Certain processes described in the art require an emulsion of two liquids (e.g., U.S. Pat. Nos. 4,293,459 and 5,478,365). In such cases the presence of hot (liquefied) heavy hydrocarbon is required with a strong emulsifying agent There the hydrocarbon is not present as solid particles but must itself be liquefied.
However, if the DAU rock or coke could be formed into an aqueous, pumpable fluid, the fuel could be transported easily and at low cost through conventional pipelines. One should also note that the presence of water in the pumpable fluid along with the feed is advantageous in power generation, where water is frequently required for processes such as steam reforming.
There is therefore is a need for a method of forming coke or DAU rock into an aqueous, pumpable fluid.
Certain aqueous slurries of coal and coke are known. These slurries are formed by combining coal or coke with an aqueous fluid containing polymers such as gum tragacanth, gum arabic, guar gum, xanthan gum, starch, CM-cellulose, unhydrolyzed gelatin, carageenan, and hydroxymethyl cellulose. Treatment solutions known in the art may also contain anionic or non-ionic surfactants such lignosulfonate and polyethylene oxide surfactants. Such treatment solutions have surfactant and polymer concentration in the range of about 0.5 wt % (about 5,000 ppm) to about 5 wt %.
One object of the present invention is the production of an aqueous treatment solution having reduced polymer concentration alone that is capable of forming DAU rock, coke, and mixtures thereof into a pumpable fluid.
One embodiment is a method for forming an aqueous, pumpable admixture, by (a) admixing carbonaceous solid particles less than 177 microns in size wherein the solid carbonaceous particles are selected from the group consisting of coke, DAU rock, and mixtures thereof, and an aqueous treatment solution wherein the amount of treatment solution ranges from about 20 wt % to about 60 wt % of the total weight of carbonaceous solid and treatment solution and wherein the aqueous treatment solution comprises a water-soluble polymer capable of viscosifying water, the polymer being present in an amount ranging from about 10 to about 500 ppm; and then (b) subjecting the admixture to shearing forces for a time sufficient to reduce the admixture""s viscosity to below about 20,000 cPs at ambient temperature (25xc2x0 C.).
Another embodiment is an aqueous, pumpable composition having a viscosity below about 20,000 cPs comprising a carbonaceous solid selected from the group consisting of coke, DAU rock, and mixtures thereof and an aqueous treatment solution comprising a water soluble polymer capable of viscosifying water, the polymer being present in an amount ranging from about 10 to about 500 ppm, wherein the concentration of the carbonaceous solid in the treatment solution ranges from about 40 wt % to about 70 wt % based on the weight of the carbonaceous material and water.
The invention may comprise, consist or consist essentially of the elements or steps recited herein and may be practiced in the absence of a limitation not disclosed as required.